Integrated circuit digital devices, e.g., digital processors such as, for example but not limited to, microprocessors, microcontrollers, digital signal processors (DSP), programmable logic array (PLA), application specific integrated circuit (ASIC) and the like, are becoming smaller and with fewer external input-output (I/O) signal connections (e.g., pins or leads) for both cost and space considerations. Typically an integrated circuit device may be in an integrated circuit package having a plurality of external connections. At least two of these external connections must be used for power and ground, e.g., VDD and VSS, respectively. The remaining few external connections are left for I/O signals. For example, the Serial Peripheral Interface (SPI) Bus requires four external signal connections, the Universal Serial Bus (USB) requires two external signal connections and also may require two external power connections, the Inter-Integrated Circuit (I2C) requires two external signal connections, and The Controller Area Network (CAN) may use a two wire twisted pair bus.
The integrated circuit devices may benefit from additional device functions, e.g., external memory, high speed interfaces, sensors, peripherals, etc. Memory may be, for example but not limited to, one time programmable (OTP), electrically programmable read only memory (EPROM), electrically erasable and programmable read only memory (EEPROM), FLASH memory, static random access memory (SRAM), dynamic random access memory (DRAM), etc. High speed interfaces may be, for example but not limited to, Ethernet, Universal Serial Bus (USB), Firewire, and the like. Sensors may be used to measure, for example but not limited to, pressure, temperature, humidity, voltage, current, frequency, time, radiation, pH, etc. Peripherals may be used to capture, for example but not limited to, video, audio, radar, infrared, ultrasonic information, etc. Integrated circuit package size for these devices is being more critical from both cost and printed circuit board space requirements.